Push-button control of signal seeking receivers



Feb. l2, 1946. M. ca.. NxcHc-JLSN, JR

PUSH BUTTON CONTROL OF SIGNAL 'SEEKNG RECEIVERS Filed OCT.. 5, 1944 Patented Feb. 12, 1946 PUSH-BUTTON CONTROL OF SIGNAL SEEKING RECEIVERS Madison G. Nicholson, Jr., Snyder, N. Y., assignor ,to Colonial Radio Corporation, Buialo, N. Y.

Application October 5, 1944, Serial N0. 557,312

(Cl. Z50- 40) 13 Claims.

This invention relates te signal seeking receivers, and more particularly to push button control thereof.

In signal seeking receivers of the usual co-nstruction thereV is provided a motor-operated tuner which may be set in motion by means of a push button when the operator desires t receive aY station. The tuner will then scan the spectrum of the receiver until an incoming signal of predetermined strength is received,'when the action of the receiver in responding to such incoming signal interrupts the operation of the tuning motor. The receiver will remain tuned to the received signal until the operator again pushes the button, which starts the tuning motor in operation again.

In the usual form of such receiver the operator has no control over what station will be selected by the receiver other than a control of the motor stopping means in response to the strength of signals. Some form of variablepbias is usually provided which enables this control to be obtained, but it is undesirable for unskilled operators to have access to such control and, therefore, for most purposes such receivers select signals without any control by the operator, and the receiver will stop 0n the first signal of predetermined strength which is encountered. as the tuning is varied. For the purposes of this invention, a receiver of this type is termed random signa1 seeking.

Under certain conditions it is desirable to enalolek the operator to select a particular station to which he wishes to listen, while still Vemploying the signal seeking principle. This is desirable, for instance, in metropolitan areas Where a great many stations may be received with sufficient strength to stop the tuning, and where the listener prefers to listen only to certain particular stations. It is also desirable when a listenerhas a particular program in mind vwhich is on a particular station at a particular time, and when the listener does not wish to lose time in going through the entire spectrum in a search for the desired station.

In accordance with my invention I have provided means whereby particular stations may Vbe selected by individual push buttons, but in which the receiver still operates on the signal seeking principle and does not require mechanical adjustments, such as the setting of cams and sectors in mechanically operated push button receivers, and in which the receiver, like the usual form of signal seeking receiver, will tune itself exactly tothe incoming signal. I term a receiver according to this invention "preselective signal seeking, to distinguish from random signal seeking..

.Among the objects of my invention may be mentioned thel following: To provide a signal seeking receiver which may be operated like the conventional push button operated receiver to select only particular ones of the stations within range.

To provide a receiver of the class described which may, at the users option, be operated like a conventional push button receiver to select a particular one Aof a number of predetermined stations, or which may operate as the usual type of random signal seeking receiver, scanning the entire spectrum and tuning in whatever may be on the air at the moment.

Itis still a further object of this invention to provide such a receiver in which no adjustments are required by the operator in operating either as a push button receiver or as a conventional signa1 seeking receiver.

It is still a further object of my invention to provide such a receiver 'in which the push buttons -and signal-seeking button may be located at'af point remote from the receiver itself.

Still other objects and vadvantages of my invention willl be apparent from the specification.

The features of novelty which I believe to be characteristic ofmy invention are set forth with particularity in the appended claims. My invention itself, however, both as to its fundamental principles Yand as to its particular embodiments, will best be understood by reference to the speciiication and accompanying drawing, in which the single figure is a circuit diagram of a receiver inaccordance with my invention.

' As previously stated, the usual signal seeking receiver is provided'with a single button control. When the operator pushes this button, the tuner motor is set'in operation and the receiver will scan the spectrum included within its range until ittunes in a signal of predetermined strength. Thereupon the tuning is stopped andthe receiver remains in tune .with the signal which stopped it until the operator again pushes the button starting the tuning, whereupon it will move on until it encounters the next signal of predetermined strength and will stop there.

Receivers of this type, when operated in favorable receiving locations, may tune in and stop on as many as thirty or more stations in the spectrum, and if the operator Wishes to receive a particular station, he may not wish to spend time going through the spectrum to locate it. I, therebreaking up the tuning into two sequential steps,

the first of which consists in tuning, not to incoming signals, but to a locally-generated oscillation having a frequency differing from the desired station frequency by a small amount, preferably less than 10,000 cycles, and lying in front of the desired station frequency, considering the direction of tuning of the receiver. u A y A y Thus, if the receiver tunes from the low frequency end to the high frequency jend of the spectrum, the local oscillator frequency will be set less kthan 10,000 cycles below that `of the desired station frequency. i

On first pushing the button for the desired station, this local oscillator is set into operation at the preset frequency. Simultaneously, the sensitivity of the receiver is decreased tol a point such that it is unresponsive to incoming signals, `but will respond only to the local loscillator 'frequen'cy.

The receiver will then begin to scan thejspectrum but will not stop on incoming signals. It will continue to operate until the receiver is tuned to the local oscillator frequency. At this point tuning is interrupted `by the response of the receiver to the oscillator frequency. The receiver is now tuned to a frequency less than one channel from the desired station.

As soon as this action is completed andthe receiver tuning is momentarily stopped, the special oscillator is put out of action, the sensitivity of the receiver is restored, the motor circuit is again closed by special means which will be described fin Ldetail hereafter, and the receiver again begins to vary its tuning at full sensitivity. g

At this point it is verynear the tuning of the desired signal, and very little `change in `tuning is required to tune .the desired signal exactly. When this occurs, the response ofthe receiver to the desired .signal `shuts off the tuner motor and the receiver vwill remain tuned to the incomingsigvnal until another button is pushed for `another desired station, or the signal seeking button is pushed, which 'sets the receiver into operation, as in the conventional lsignal "seeking receiver.A 4 VIn this latter condition, as willbe understood, this local oscillator is notused, and the receiver operates at normal sensitivity, and willjs'top at the' first signal of predetermined strength.

One way in kvvlfiich' my invention may be constructed and `operated Will now be describedwith reference to the drawing, which shows my invention as applied to a 'signal seekingreceiver of the superheterodyne type. In 'the figure, l represents the antenna which lsupplies the converter 2. This converter may be tuned by any suitable tuning instrumentality, herein diagrammatically shown las 'condenser 3. although it will be understood that other forms "of may "equally l we l`1 `be employed, such as inductance or 'permeability tuning.

The converter receives locally generated oscillations of heterodyning frequency from heterodyne oscillator 4 tuned by, variable tuning instrumentality 5 ganged with the converter tuning 3 and driven by suitable tuner motor 20. The oscillator may be a separate oscillator or it may be a part of the converter as when a pentagrid converter is used.

The heterodyned oscillations are detected and supplied to the intermediate frequency amplifier `(i and the output of the same may be detected again and amplified at audio frequency by the detectorl and audio amplifier 1, and supplied to a suitable indicator, such as loud speaker 8. So far the apparatus described is the conventional form of superheterodyne receiver familiar to those skilled in the art and which, therefore, needs no further description.

For the purpose of providing a control voltage to stop and start tuner motor 20, a portion of the output from intermediate frequency amplifier 6 may be" fed to limiter 9. Since a limiter is well known in the art, it is not believed necessary to describe it in detail. The output of the limiter may then be supplied to narrow band selector l0. Ths may take any -one of a number of suitable forms, and, for example, may be a crystal selector such as shown and described in the co-pending application of Verlis H. Wiley, Serial No, 554,470, flled September 16, 1944, owned by the assignee of this application- The band widthof Selector l0 is preferably made a small fraction of thatvof intermediate frequency amplifier 6. If the latter has a pass width vof 5,000 cycles, for example, then narrow band selector I0 may be given a band pass width of only v500 cycles. This permits the receiver to operate on signals of feeble strength even fin the presence of considerable noise and static with'out false stoppages of the tuning resulting from noise or static. This feature is claimed in the aforementioned application 'of Verlis H. Wiley and forms per se no partof this invention.

The control tube 28 may be fed by the output from narrow band selector i0, and this tube may bea th'yratron having cathode 28e, control electrode 228g, and anode 2da, the control electrode being connected to the output of narvro'wband yselector l0, and .also to ground through suitable resistance '21. The anode may be `connected to energizing winding 29u? of relay 29, and this coil maybe shunted by condenser 30, 4and 'winding '2910 may be connected to +B to provide plate voltage. w

Relay :armature 29a may be Vconnected lto ground and is spr-ing biased to back contact 23h yand 'energized to front contact 20?. Back contact '29h may be connected to the `ungfround'ecl lead .to 'the loud speaker, and serves to fmute the loud speaker when the armature is in back 'contact position. In front contactposition fthe armature closes the circuit through energizing winding of relay .30,which includes source of voltage Relay 30 may operate -two armatures 30m and 30cm, vand these larmatures ina-y 'be spring biased 'to back contact position 'and energized to front contact position. Front Vcontact 3031 may be unconnected, Back contact 3013i may be connected to one 'side of motor 26 and armature 30m .may be connected -to the other side 'of the motor through suitable source of current 39. Armature `Afilial may be connected to +B, and front contact "30'12 may be connected Ithrough'co'ndenser "34 shunted'by 'resistancei to 'cathode ilctoftube 28.

Back contact 30172 may beV connected through oscillator coil I`4s to the anode of oscillator I5. The latter may be a suitable triode having vcatho de Ic, control electrode |59, and anoder I5a. The cathode may be connected through resistance 31 to ground shunted by condenser I6, and also to contacts 22a, 221), and 22c of switches 22. Control electrode `I5g may be connected through resistance 25 to the A. V. C. line leading'to the I. F. amplifier E, and shunt resistance 24 to ground may also be provided.

Control electrode |5g may also be connected through condenser 23 to the common point of condensers I Ib, |212, and |31), from the other side of which condensers connections may be estab# lished through switches I Ia, I2a, or I3a to ground. Said switches may be operated by their associated push buttons II, I2, and I3, which constitute the individual station buttons, and their operation will be described more in detail later. It may be noted at this point, however, that, while for purposes of simplicity I have shown only three of these, as many more may be provided as desired, although ordinarily five or six would be regarded as sufficient.

The common terminal of condensers I Ib, |212, and |317 and condenser 23 may be connected through coil Mp to ground, and coils Ida, and Ms are preferably coupled to form a feed-back circuit for oscillator I5. The oscillator frequency will be determined by the setting of condensers II b, I2b, and |31), the same being variable', but not provided with operating controls for the user. They are preferably set in a manner which will be hereinafter described and thereafter left alone until it becomes necessary to reset thereceiver for different stations.

It will be noted that when armature 30112 is 'closed against back contact 301m, B voltage is applied through resistances 38 and 31 to ground and also through resistance 38 to conductor 4I. A portion of the oscillator voltage may be picked Yup by inductance I4a coupled to coil |4p and I4s and thence applied to antenna I through suitable condenser 40.

Push buttons II, I2, and I3 are arrangedvin the well-known interlocking manner so that only one may be depressed at a time, and the depression of any one releases any other which happens to be depressed. In additionV to buttons II, I2, and I3, which are set for particular stations, there may be provided another push 'button' |'1 operating to close switch 2U, having its movable contact connected to ground through conductor 42, to which are also connected thevmovable contacts of switches 2|, 22a, 22h, and 22o. The fixed contacts of switches 22a, 221), and Y22e may be connected to conductor 4I and the fixed contact of switch 2| through resistance I8 to cathode 28oA of control tube 28.

Condenser I9 may be connected from one terminal of resistance I8 and through switches 20 and 2| to the other terminal of resistance I8. The tuning motor ordinarily is arranged for operation in only one direction, and theV tuning instrumentality for 360 rotation, and. ordinarily a switch (not shown) will be provided for shorting out the signal seeking operation on thereturn half of the 360 rotation of the tuning instrumentality. This may be done very simply; for example, by providing a switch which short circuits the input to the receiver or opensrthe space' current path of tube 28 during the return half of the rotation of the tuning instrumentality.

Condensers IIb, I2b,and v|31) are preferably so adjusted thatwhen the particular button associated therewith is closed, the voscillator generates a wave of a frequency differing by a small amount, say a few thousand cycles, from the particular station desired to be received by the operation of that button, and in such direction that the oscillator frequency lies ahead of the desired station, that is, so that oscillator frequency is tuned in before the desired station would be tuned in.'

Buttons II, I2, and I3 are arranged with suitable interlocking means such as slider 2Ia so that upon depression of any button, switch 2| is momentarily opened in passing. This interrupts the plate circuit of tube 28, causing deionization thereof if it happens to be ionized, interrupting the current through relay winding 291.0, and permitting armature 29a to fall back against back contact 291i, thereby muting the loud speaker. i

This also interrupts the current in relay energizing winding 30u), permitting armatures 30111 and 3Ila2v to fall back'against their back contacts 30171 and 30192. Closure of 30m against 30111 closes the motor circuit and starts the motor in operation, varying the tuning. Closure of 30m2 against 30b2 supplies -I-B voltage to the plate circuit of oscillator I5. Closure of any button of the series II, I2, and I3 also momentarily closes one of the switches 22a, 22h, or 22e. -This momentarily applies ground to the cathode of oscillator I5, removing the cut-off bias otherwise applied by the I. R. drop through resistance 31, and the oscillator I5 will be set into operation at the frequency determined by button II, I2, or I3. Opening of switches 22a., 221), or 22o immediately thereafter restores the bias on tube I5, but it continues to oscillate, although it will not start with the bias applied.

At the same time, a negative voltage is developed on control electrode I5g and applied to the A. V. C. line to substantially reduce the sensitivity of the receiver to a value such that it is no longer responsive to incoming signals, but only to the special oscillator I5. The receiver willcontinue to vary its tuning until it tunes in the oscillator frequency, at which time a Voltage is applied from narrow band selector I to control electrode 28g of tube 28.

This is sufficient to ionize the tube, which begins to pass plate current, closing armature 29a. against front contact 29j, and thereby energizing relay Winding 30u: and closing armatures 30a1 and 30112 against front contacts 30h and '30f2,-interrupting the motor circuit and the plate amount. Application of -I-B voltage to contact Sofa applies a surge of positive Voltage to cathode 28e of tube 28, which extinguishes this tube and, therefore, armatures 29a, 35111, and 30112 are released against back contact position. This energizes the motor circuit again, and the motor begins to operate, tuning from the oscillator frequency toward the desired signal frequency,

Now, however, the oscillator I5 does not begin to oscillate as it did before, because of the factfthat'switches 22a, 2212, and 22C are open, and a cut-off bias is applied to the oscillator, derived fr om the connection of cathode I5c to the commonY point of resistances 31 and 38, so the tuner will continue to turn until the desired station is `tuned in if it is on the air, and when the desired station is tuned in, the narrow-band selector applies a voltage to control electrode 28g, which ionizesc this tube for the second time, thereby closing armatures 29a, 30m, and130a2 against their respective front contacts, .stopping the motor.

The closure of 30a2 against its front contact again applies -I-B voltage to condenser 34, but since this has not had suicent time to discharge from the previous application .of +B voltage, the surge which reaches cathode 28e is not sufficient to extinguish tube 28, and the relays hold in front contact position with the receiver on tune to the desired station.

It is important to note at this point that the tuning of oscillator I5, as determined by buttons II, I2, and I3, must be made sufficiently close to the desired station frequency so that the receiver will not pick up another station in between the oscillator frequency and the desired station frequency, as this would cause the receiver to stop on the intervening station. It will also be noted that, while this operation is rather lengthy to describe, it occurs veri7 quickly, the stoppage on the oscillator frequency being only momentary, and being evidenced only by a slight clicking of the relays. y

It will be noted that the tuning of oscillator I does not in any Way interfere with the stopping of the tuning when the desired station is tuned exactly, this preliminary stoppage on the oscillator setting being a means of quickly arriving at a point just ahead of tuning in the desired station. The foregoing description applies for operation of any one of buttons II, I2, andv I3, except that the local oscillator frequency will be direrent in each case.

The adjustment of the local oscillator frequency for the desired stations is an operation which is best performed by a service man with the aid of a second (not signal seeking, however) receiver. One procedure is to tune in both the desired station and the local oscillator on the second receiver, to adjust the local oscillator by varying condenser IIb, I2b, orA I3b, as the case may be, to zero beat for the desired station, and then to detune to a small degree so as to shift the oscillator frequency ahead of the desired station frequency bya small amount, not

more than l0 kc., preferably somewhat less, say

6 to 8 kc.

To provide for purely signal seeking operation which will receive any station on the air', the operator presses button I'I. Upon pushing signal seeking control button Il, the rst action which occurs is the release of any of buttons II, I2, or I3, which may be closed, thus opening the corresponding switch, IIa, I2a., or I3a, and closing switch 20.

At the same time switch 2| is opened, opening the plate circuit of tube 28, and deionizing it if it happens to be ionized. Deionization of tube 28 allows the relays to fall back to back contact position, closing the motor circuit and starting the tuning.

Oscillator I5 will not be operated because switches 22a, 22D, and 22o are open and cathode I5c is biased to cut-off by its elevated potential derived from connection to the common point of resistances 3l and 38. Therefore, the tuning will continue until an incoming signal is tuned in having sufficient strength to ionize tube 28, at which point the relays will be attracted to. front contact position, the motor circuit will be opened, andtuning will be stopped.

v-lVIoVement of armature 30cm to front contact 30j: again applies B voltage to condenser 34 and throughit to cathode 28e, but since switch 20 is now closed (it being remembered that this switch is closed at all times except when button II, I2, or I3 is in), condenser I9 absorbs the positive surge and the cathode does not rise sufliciently to extinguish tube 28.

Therefore, the immediate reclosure of the motor circuit which occurs with buttons I I, I2, and I3 does not occur with button II, and the receiver will remain tuned to the incoming signal until button I1 is again closed, when the operation just described occurs again and the receiver moves on to the next station in the spectrum.

The switch assembly containing buttons I I, I2, I3, and I1 may be made up of a casing containing slotted button plungers Ilc, I2C, I3c, and I'Ic, and plungers IIb, I2b, and I3?) may engage locking slider 2Ia. and plain slider 20a, which pass through slots therein, both sliders being moved to the right when a controlling button is pressed. Note that button I'I does not engage or operate slider 20a. When button II, I2, or i3 is fully depressed, both sliders 20a and 2 Ia are iirst moved to the right, opening switches 2i) and 2 I, and slider 2Ia then returns to initial position as, engaging one of fingers 2 Ib with slot Zic of the respective plunger, latching the same in depressed position, closing switch .2I, and holding slider 20a at the right-hand position, and keeping switch 20 open. Note also that plunger I'Ia has no latching slot 2 Ic and, therefore, does not latch in.

Itis clear that all of the apparatus herein described may be incorporated in the chassis of the receiver if desired, but it will also be understood that the apparatus lends itself readily to a remote control receiver. In this instance the switch assembly may be a separate unit to be mounted at any convenient or desired location, and connected to the chassis by cable, so that in an automobile the chassis might be located under the front seat or in the trunk, and the switch assembly on the steering column or dash.

Also, the push button and special oscillator and associated parts may be made as a special unit available. separately to be connected to a conventional signal seeking receiver so as to convert it for push button operation.

While I have shown and described my invention as'applied to a superheterodyne receiver, it will be understood that it may equally well be applied to receivers of the T. R. F. type.

While I have shown and described certain preferred embodiments of my invention, it will be understood that modifications and changes may be made without. departing from the spirit and scope thereof, as will be clear to those skilled in the art.

In this application I have explained the principles. of' my invention and the best mode in which Iv have contemplated applying those principles, so as to distinguish my invention from other inventions; and I have particularly pointed out and distinctly claimed the part, improvement, or combination which I claim as my invention or cliscovery.

I claim:

1. The combination with a signal seeking receiver, having a variable tuning instrumentality, electrical power means for varying said tuning instrumentality, and means operated by `said receiver for stopping the variation of tuning in respense to reception of an incoming signal of preceiver,*having a variable tuningeinstrumentality,

determined strength; of apushubutton signal selector including a plurality of push buttons presettable for the selection of individual desired stations respectively, an oscillator, means operated by said push buttons for setting the oscillator into oscillation at a frequency immediately adjacent to desired station frequency, means for interrupting both the tuning variationand operation of said oscillator when said receiver is tunedz to said oscillator, and means operated by said receiver for yrestarting said tuning variation immediately thereafter.

2. The combination with a signal seeking receiver, having a variable tuning instrumentality,

lator into oscillation at a frequency'immediately adjacent to desired station frequency and ahead 4of the desired station frequency in relation to the direction of frequency change in tuning, means for interrupting both the tuning variation and operation of said oscillator when the said. receiver is tuned to said oscillator, and means operated by said receiver for restarting said tuning variation immediately thereafter.

3. The combination with a signal seeking receiver, having a variabletuning instrumentality,

electrical power means for varying said tuning instrumentality, means operated by said receiver for stopping the variation of tuning in response to reception of an incoming signal of predetermined strength; of a push button signal selector including a plurality of push buttons presettable for the selection of individual desired stations respectively, an oscillator, means operated by said push buttons for setting the oscillator into oscillation ata frequency immediately adjacent to desired station frequency, means for increasing the required signal strength level necessary to stop said tuning variation while said oscillator is in operation, means for interrupting both the tuning variation and operation of said oscillator vwhen said receiver is tuned to said oscillator, and means operated by said receiver for restarting the tuning variationimmediately thereafter.

4, The combination with a signal seeking receiver, having a variable tuning instrumentality, electrical power means for varying said tuning instrumentality, and means for stopping the variation of tuningin response to receptionof an incoming signal of predetermined strength; of a push button signal selector including a plurality of push buttons presettable for the selection of individual desired stations respectively, an oscillator, means operated by said push buttons for setting the oscillator into oscillation at a frequency immediately Vadjacent the desired station frequency, means for increasing the required signal strength level necessary to stop said tuning variation to a value in excess of any incoming signal while said oscillator is in operation, means for interrupting both the tuning variation and oscillation of said oscillator when said signal is tuned to said oscillator, and means operated by said receiver for restarting the tuning variation immediately thereafter.

5. The combination with a signal seeking reelectrical power` means for; varying said tuning instrumentality, means for stopping the variation of tuning in response to reception of an 4incoming signal of predetermined strength; of a push button signalselector including a plurality of push buttons presettable for the selection of individual desired stations respectively, anV oscillator, means operated by said push buttons forl setting the oscillator into oscillation at a frequency immediately adjacent to desired station frequency,V said means including a biasnormally suiiicient to prevent said oscillator from starting, but insufficient to stop it after starting, and means for removing said bias .on operation of any push button; means for increasing the required signal strength level necessary to stop said tuning variation to avalue in excess of thatof any incoming signal'while'said oscillator is in operation, means for interrupting both the tuning variation and oscillation of said oscillator when said signal is tuned to said oscillator, and means operated by said receiver for restarting the tuning variation immediately thereafter. f 1

6. The combination with a signal seeking receiver, having a variable tuning instrumentality, electrical power means for varying said tuning instrumentality, means for stoppingthe variation of tuning in response to reception of an incoming signal of predetermined strength; of a push button signal selector including a plurality of push buttons presettabley for the selection of individual desired stations respectively, an oscillator, means operated byr said push buttons for setting the oscillator into oscillation at a frequency immediately adjacent the desired station frequency, meansfor increasing the required signal strength level necessary to stop said tuning variationl to a value in excess of anyA incoming signal while said oscillator is in operation, means for interrupting both the tuning variation and oscillation of said oscillator when said signal is tuned to said oscillator, means operated by said receiver for restarting the tuning variation immediately thereafter, and means for preventing restarting operation of said oscillator. A

7. The combination with a signal seeking receiver, having a variable tuning instrumentality, electrical power means for varying said tuning instrumentality, means for stopping the variation of tuning in response to reception of an incoming signal of predetermined strength; of a push button signal selector including a plurality of push buttons presettable for the selection of individual desired stations respectively, an oscillator, means operated by said push buttons for setting the oscillator into oscillation at a frequency immediately adjacent the desired station frequency, means for increasing the required signal strength .level necessary to stop said tuning variation to a value in excess of any incoming signal while said oscillator is in operation, means for interrupting both the tuning *variation and oscillation of said oscillator when said signal is tuned to said oscillator, means operated by'said receiver for restarting the tuning vari-ation immediately thereafter, Vand means for preventing the restarting of tuning variation when the receiver stops tuning upon the preselected station.

8. The combination with a signal seeking receiver, having a variable tuning instrumentality, electrical power means for varying said tuning instrumentality, and means for stopping the variation of tuning in response to reception of an incoming signal of predetermined strength, said means comprising a thyratron having a cathode, an anode, and a control electrode, and stopping the electrical power means in response to a signal of' predetermined strength; of a push button signal selector including a plurality of push buttons presettable for the selection of individual desired stations respectively, an oscillator, means operated by said push buttons for setting the oscillator into oscillation at a frequency immediately adjacent the desired station frequency, means for increasing the required signal strength level necessary to stop said tuning variation to a value in excess of any incoming signal While said oscillator is in operation, means for interrupting both the tuning variation and oscillation of said oscillator when said signal is tuned to said oscillator, and means operated by said receiver for restarting the tuning variation immediately thereaftensaid means including means for -applying a surge of positive potential to the cathode of said thyratron.

9. The combination withA a signal seeking receiver, having a variable tuning instrumentality, electrical power means for varying said tuning instrumentality, and means for stopping the variation of tuning in response to reception of anincomingV signal of predetermined strength, said means comprising a thyratron having a cathode, an anode, and a control electrode, and stopping the electrical power meansin response to a signal of predetermined strength; of a push button signal selectorA including a plurality of push buttons presettable'for the selection of individual desired stations respectively, an oscillator, means operated by said push buttons for setting the oscillator into oscillation at a frequency immediately adjacent the desired station frequency, means for increasing the required signal strength level necessary to stop said tuningvariation to a value in excess of any incoming signal while said oscillator is in operation, means for interrupting both the tuning variation and oscillation of said oscillator when said signal is tuned to said oscillator, means operated by said receiver for restarting the tuning variation immediately thereafter, said means including means for applying a surge or positive potential to the cathode of'said thyratron, and means for preventing saidl surge from deionizing said thyratron whenl the preselected stationv is tuned.

1'0. The combination. with a signal' seeking receiver, having a variable tuning instrumentality, electrical; power means for varying said tuning'instrumentality, and means for stopping the variation of'tuningv .in response tcreception of an incoming signal of' predeterminedv strength; oi a push button signalv selector including a plurality of push buttons presettable for the selection of individual desired` stations respectively, an oscillator, means operated byl said push buttons for settingl said oscillator intoy oscillation at a frequency immediately adjacent the desired station frequency, means for increasing the required signal strength level necessary tov stop said tuning variation` to a value. in excess of any incoming signal While said oscillator is in operation, means for interrupting both the tuning variation and 'oscillation of said oscillator when said signal is tuned to said oscillator, means operated by said receiver for restarting the tuning variation immediately thereafter, and additional means for starting tuning variation and preventing starting of said oscillator.

11. The combination with a signal seeking receiver, having a variable tuning instrumentality, electrical power means for varying said tuning instrumentality, and means for stopping the variation of tuning in response to reception of an incoming signal of predetermined strength; of a push button signal selector comprising a plurality of push buttonsr presettable for the selection of individual desired stations respectively, an oscillator, means associated with each of said push buttons for setting the. frequency of said oscillator immediately adjacent to the frequency of the desired station, means for initiating operation ofV said oscillator upon closure of any station selector button, means for reducing the sensitivity of said receiver while said oscillator is in operation, means for applying oscillations from said oscillator to the input of said receiver whereby variation of tuning will be interrupted When the receiver is tuned to the oscillator frequency, means for restarting said Variation of tuning immediately upon termination thereof, means for restoring the receiver sensitivity, and means for preventing operation of said oscillator after said restarting;

12. The method of tuning a radio receiver which comprises'generating at said receiver currents of a frequency adjacent to the frequency of any one of a plurality of desired station frequencies, conditioning the receiver to be affected only by the currents generated at said receiver, impressing the said currents corresponding to said selected frequencies on said receiver, adjusting the receiver tuning elements, utilizing the current, in Asaid receiver to terminate the adiustment of said tuning element when the currents generated at said receiver have been tuned in, thereafter conditioning the receiving apparatus so as to be aiected only by incoming signals,

again varying the tuning of the receivingl apparatus, and utilizing the output of the receiving apparatus at the desiredY frequency toA terminate variation of its tuning,

13. The method of tuning radio receiving apparatus to any selected one of a plurality of different frequencies, which comprises generating at the receiver currents of a frequency adjacent to the preselected frequency but differing therefrom by not more than 10 kc., simultaneously conditioning the receiving apparatus to be affected only by currents generated at the receiver, impressing such generated currents on the receiving apparatus, varying the tuning of the receiving apparatus, utilizing the output of the receiver when tuned to said generated currents to stop the variation. of tuning, immediately there- `after conditioning the receiving apparatus Vto respond only to received signals, again varying the tuning, and. utilizing the output of the receiving apparatus to terminate variation of its tuning. MADISON G.NICHOLSON, JR. 

